This document describes a proposal to investigate: (1) the development of malignant lymphoma in homosexual men with persistent, generalized lymphadenopathy (PGL) and AIDS-like immune dysfunction (acquired immunodeficiency syndrome); (2) factors responsible for the development of this state; and (3) the development of PGL or AIDS or malignant lymphoma in sexual contacts of these patients. Patients will be examined at 6 month intervals, and have serial lymph node biopsies and blood specimens taken. The lymph nodes will be investigated for morphologic expression, and for quantitative and qualitative changes in lymphocyte populations. In addition, DNA content analysis, oncogene expression, chromosomal karyotypes, and staining for various viral antigens (EB, CMV, HTLV) will be performed on the nodes. Serial evaluation of immunologic function will be performed at 6 monthly intervals, including B and T lymphocyte numbers and subsets, Interleukin I and II levels, natural killer and macrophage cytotoxicity. Serologic evidence of infection to a variety of agents (CMV, EB, HTLV, Hepatitis B, toxoplasmosis) will be studied. In addition, a careful epidemiologic evaluation will be performed. All of these parameters will be evaluated serially, in order to note changes which may be associated with the development of lymphoma. Patients will be compared to friend controls who are sexual contacts and with other homosexual controls by means of serial evaluation at six month intervals, with epidemiologic questionnaire, viral serologic and immunologic studies, identical to those performed on the patients, in order to discover those factors responsible for the development of the lymphadenopathy syndrome, or for lymphoma, or for AIDS in the normal homosexual population.